If it's your first trip to Florence, I suggest staying in the city itself. There is something wonderful about walking outside your hotel to find this beautiful city just beyond. And, if you stay in the city center, which is what I recommend, it's a short stroll to shops, cafes, art galleries and museums.
So, why would you stay outside the city? Perhaps you've seen many of Florence's attractions and want to be away from the touristy busyness of Florence. Maybe, you wish to be closer to other activities you will pursue - wine tasting and olive oil tasting, culinary classes, visiting the Ferrari Factory and similar pursuits. Perhaps, it's your honeymoon and you want a quiet, romantic vacation. Most of the hotels located outside the city offer a shuttle to/from the city center - some are complimentary and others do charge a fee., If you will stay in a private villa, make sure you know what the local transportation is like - trains and proximity to a train station, a rental car or hiring a private car and driver.
Wherever you stay, you will love the culture and beauty of Florence, Italy's Renaissance city.
Italian Ventures, your Virtuoso® travel agency, in Clovis, Fresno, & Kingsburg, CA